Digestion involves the breakdown of food materials into molecules that can be delivered to and utilized by individual cells of the body. These molecules may serve as energy sources; they may provide essential chemical elements, such as calcium, nitrogen or iron; or they may be complete molecules, e.g., certain amino acids, fatty acids and vitamins, that the cells need but cannot synthesize themselves. Digestion which incorporates the processes of breakdown and assimilation of food materials as well as the elimination of undigestable waste material takes place in a long convoluted tube that extends from the mouth to the anus, known as the gastrointestinal (GI) tract. The GI tract begins with the oral cavity, the mouth, and continues to include the, pharynx, esophagus, stomach, small intestine, large intestine and anus. The GI tract, from beginning to end, has foucalr tissue layers: (1) the mucosa, which is the innermost layer, is made up of columnar epithelial cells that are in direct contact with ingested materials and facilitate fluid and electrolyte transport and digestion and absorption of nutrients, an underlying basement membrane consisting of connective tissue and a thin layer of smooth muscle; (2) the submucosa, which is the second innermost layer, is made up of connective tissue containing small clusters of nerve cells and nerve fibers, and blood and lymph vessels; (3) the muscularis externa, which is the third innermost layer, is made up of two separate layers of smooth muscle tissue oriented in opposing directions and containing a vast network of nerve cell clusters and nerve fibers sandwiched in-between these layers; and (4) the serosa, which is the outermost layer consisting of a coating of connective tissue that is in contact with the environment of the peritoneal cavity of the abdomen.
Along most of the GI tract, the muscularis externa is made up of two opposing layers of smooth muscle, the inner layer, in which the cellular orientation is perpendicular to the long axis of the gut, and the outer layer, in which cellular orientation is parallel to the long axis of the gut. Coordinated contractions of these muscle layers produce ring-like constrictions that mix food, as well as wave-like motions, known as peristalsis, that move food along the GI tract. (See FIG. 29). At several points, the circular layer of muscle thickens into heavy bands forming valve-like constrictions called sphincters, which by relaxing and contracting, act to regulate the passage of food from one area of the GI tract to another.
Breakdown and assimilation of nutrients from food materials is accomplished chiefly by the highly coordinated activities of the stomach and small intestine. The stomach is influenced by both the nervous and endocrine systems. Anticipation of food and the presence of food in the mouth stimulate churning movements of the stomach and the production of gastric juices. When food reaches the stomach, its presence causes the release of the hormone gastrin from gastric endocrine cells into the bloodstream. Gastrin acts on the cells of the stomach to increase their secretion of gastric juices.
Food is converted in the stomach to a semiliquid mass as a result of gastric juices, including pepsin, hydrochloric acid and the churning motions. The food is then emptied into the small intestine, where the breakdown of food is completed. The resulting nutrient molecules are then absorbed into the circulatory system, from which they are delivered to the individual cells. The small intestine contains a variety of digestive secretions, some produced by the intestinal cells and some by the pancreas and liver. Other epithelial cells, the goblet cells of the mucosa, secrete mucus. The digestive activities of the small intestine are coordinated and regulated by hormones. In addition to hormonal influences, the intestinal tract is also regulated by the autonomic nervous system, which is involved in the secretion of digestive enzymes and in contraction. Thus, a complex interplay of stimuli and checks and balances serves to activate digestive enzymes, adjust the chemical environment and regulate the movement of ingested materials in the intestines.
The large intestine is involved in the absorption of water, sodium and other electrolytes. Some of its epithelial cells secrete mucus, which lubricates undigested food residue. Large amounts of water enter the stomach and small intestine by osmosis from body fluids or as secretions of the glands lining the digestive tract. When the absorption process is interfered with and/or secretions from the mucosal glands becomes enhanced, as in diarrhea, severe dehydration can result.
Functional bowel disorders involve abnormal motility and secretion within organs of the GI tract, and are characterized by abdominal discomfort/pain. The Criteria for these disorders are summarized by gastroenterologists in the ‘Rome II criteria’ (See, for example, Rome II Diagnostic criteria for the Functional Gastrointestinal Disorders, Second Edition, Senior Editor Douglas A. Drossman, M.D., Management Services, McLean, Va. (2000)). Based on these criteria the disorders are common and include, but are not limited to, functional dyspepsia, irritable bowel syndrome (IBS), gastroesophageal reflux disease (GERD), non-erosive reflux disease (NERD), and chronic constipation (including colonic inertia, idiopathic pseudoobstruction). GERD is extremely prevalent, is usually associated with non-cardiac chest pain and may be treated with acid-suppressing agents and prokinetic agents. IBS is characterized by the presence of reoccurring constipation and/or diarrhea, which can be associated with gaseous distention/bloating and abdominal discomfort/pain (Thompson, W. G. and Heaton, K. W. Gastroenterology 1980, 79, 283-288). The onset of the pain of IBS is associated with a change in the frequency and/or form of stool and can be relieved by defecation. IBS is an extremely prevalent condition that occurs to varying severity in 10-15% of the population (Saito, Y. A.; Schoenfeld, P.; and Locke, G. R. Am. J. Gastroenterol. 2002, 97, 1910-1915). The pain may be treated with smooth muscle relaxants and antidepressants (Jackson, J. L.; O'Malley, P. G.; Tomkins, G.; Balden, E.; Santoro, J.; and Kroenke, K.; Am. J. Med. 2000, 108, 65-72; Jailwala, J.; Imperiale, T. F.; and Kroenke, K.; Ann. Intern. Med. 2000, 133:136-147; Akehurst, R. and Kaltenthaler, E. Gut 2001, 48, 272-282; Poynard, T.; Regimbeau, C.; and Benhamou, Y.; Aliment Pharmacol. Ther. 2001, 15, 355-361). Severe diarrhea predominant IBS is treated by alosetron, whereas constipation predominant IBS is treated by tegaserod. Functional dyspepsia is a disorder of the upper GI tract with symptoms exacerbated by a meal and associated with early satiety, nausea and vomiting. Although its etiology is unknown, prokinetic agents may relieve the symptoms of IBS. In some patients there is overlap in symptoms between GERD/NERD, functional dyspepsia and IBS. Treatments for functional bowel disorders, such as IBS, have low efficacy and are associated with adverse effects. For example, alosetron is approved by the FDA on a risk management program because it is associated with an increase in ischemic colitis. No treatments effectively alleviate pain in functional bowel disorders.
In addition to functional disorders, inflammatory bowel diseases (IBD) are common and include ulcerative colitis (UC) and Crohn's disease (CD). Although there may be a genetic component to CD, the etiology of both UC and CD is unknown. UC is a diffuse mucosal disease of the colon, characterized by inflammation and ulceration, which is associated with diarrhea and abdominal cramping. The mucosal inflammation progresses from the rectal area to eventually extend through the large bowel. CD is a transmural inflammation that most frequently involves the distal small bowel and colon. The inflammation can result in ulcers of varying involvement and in severe cases can result in transmural scarring and chronic inflammation. Both infectious and dysregulated immune functions may contribute to disease onset. Therapies for IBD include corticosteroids, immunosuppressives (azathioprine, mercaptopurine, and methotrexate) and aminosalicylates (5-ASA). These therapies involve suppression of the immune system by mimicking corticosteroids, or have unknown mechanisms of action. Oral corticosteroid use is associated with serious adverse effects, whereas immunosuppressives and aminosalicylates are only moderately effective. Infliximab (a chimeric monoclonal anti-tumor necrosis factor antibody) is effective in CD, however, its use is associated with the presence of antibodies, which reduce its efficacy. There are currently no treatments that target the motility and secretory abnormalities or painful sensation that are associated with gut inflammation.
The cysteine rich proteins known as Prokineticin 1 (PK1) and Prokineticin 2 (PK2), as well as variants, fragments and molecules having PK activity, have been identified. PK1 and PK2 have been shown to contract gastrointestinal smooth muscle (Li, M.; Bullock, C. M.; Knauer, D. J.; Ehlert, F. J.; and Zhou, Q. Y., Mol. Pharmacol. 2001, 59, 692-698), and suppress feeding (Negri, L.; Lattanzi, R.; Giannini, E.; De Felice, M.; Colucci, A. and Melchiorri, P. Brit. J. Pharmacol. 2004, 142, 181-191). PK1 and PK2 act on both PK1 and PK2 receptors, and limited structural changes of C-terminal cysteine-rich regions of these related PKs are tolerated. For example, chimeric PKs, where the cysteine-rich domains of PK1 and PK2 were exchanged between the two and a splice variant of PK2 that included a 21 residue insertion in its C-terminal domain retained activity (Bullock, C M; Li J. D.; Zhou, Q. Y.; Mol. Pharmacol. 2004, 65(3), 582-8). A PK variant binds to receptors of primary sensory neurons, and results in an intense sensitization of peripheral nociceptors to thermal and mechanical stimuli (Mollay, C.; Weschelberger, C.; Mignogna, G.; Negri, L.; Melchiorri, P.; Barra, D.; Kreil, G.; Eur. J. Pharmacol. 1999, 374, 189-196; Negri, L.; Lattanzi, R.; Giannini, E.; Metere, A.; Colucci, M.; Barra, D.; Kreil, G.; Melchiorri, P.; Brit. J. Pharmacol. 2002, 137(8), 1147-54).
PK1 induces proliferation, migration and fenestration in capillary endothelial cells derived from endocrine glands. The expression of PK mRNA has been observed in steroidogenic glands, ovary, testis, adrenal and placenta. (LeCouter, J.; Kowalski, J.; Foster, J.; Hass, P., Zhang, Z.; Dillard-Telm, L., Frantz, G., Rangell, L.; DeGuzman, L.; Keller, G. A.; Peale, F.; Gurney, A.; Hillan, K. J.; Ferrara, N. Nature 2001, 412 (6850), 877-84). In 2002 the identification of the PK1 receptor provided a novel molecular basis for the regulation of angiogenesis in endocrine glands (Masuda, Y.; Takatsu, Y.; Terao, Y.; Kumano, S.; Ishibashi, Y.; Suenaga, M.; Abe, M.; Fukusumi, S.; Watanabe, T.; Shintani,. Y.; Yamada, T.; Hinuma, S.; Inatomi, N.; Ohtaki, T.; Onda, H.; Fujino, M.; Biochem. Biophys. Res. Commun. 2002, 293(1), 396-402; LeCouter, J.; Lin, R.; Ferrara, N.; Cold Spring Harb Symp Quant Biol. 2002, 67, 217-21). For example, adenoviral delivery of PK1 to the mouse testis results in a potent angiogenic response (LeCouter, J.; Lin, R.; Tejada, M.; Frantz, G.; Peale, F.; Hillan, K. J.; Ferrara, N. Proc. Natl. Acad. Sci. USA. 2003, 100, 2685-90). Recently, it was shown that PK1 mRNA is not normally expressed in colorectal normal mucosa but is detected in colorectal cancer cells (Goi, T.; Fujioka, M.; Satoh, Y.; Tabata, S.; Koneri, K.; Nagano, H.; Hirono, Y.; Katayama, K.; Hirose, K. and Yamaguchi., Cancer Res. 2004, 64, 1906-1910).
Thus, PK1 receptor modulators, and in particular PK1 receptor antagonists, may be useful in the treatment and prevention of various mammalian disease states, for example, visceral pain that is associated with IBS and IBD. Additionally, PK1 receptor modulators, and in particular PK1 receptor antagonists, may be useful for the treatment of GERD or other forms of secretory diarrhea. Additionally, PK1 receptor modulators, and in particular PK1 receptor antagonists, may be useful in treating cancer-specific angiogenesis factor in the large intestine and reproductive organs.
WO200236625 discloses PK1 and PK2 polynucleotides and polypeptides and uses thereof.
U.S. 20040156842 and corresponding U.S. Pat. No. 6,485,938 disclose the use of peptide antagonists of PK1 and PK2 to treat inflammation in the intestine. The references disclose that the antagonists include antibodies that specifically bind with PK1 and PK2 and receptors that bind to amino acid sequences disclosed therein.
WO2004087054 discloses methods of modulating gastric acid or pepsinogen secretion by administering a prokineticin receptor antagonist to alter one or more indicia of gastric acid secretion. The reference discloses that the prokineticin receptor antagonist is a modified version of a prokineticin from any species that contains an amino acid sequence at least 80% identical to an amino acid sequence disclosed therein.
None of the references disclose or suggest a small molecule modulator of the PK1 receptor. The identification of such modulators should facilitate the development of novel therapeutics for disorders that involve impaired or enhanced gastrointestinal motility and/or secretion.
It is an aspect of the present invention to provide PK1 receptor modulators, and in particular, PK1 receptor antagonists. It is also an object of the invention to provide a method of treating or ameliorating a condition mediated by the PK1 receptor. And, it is an object of the invention to provide a useful pharmaceutical composition comprising a compound of the present invention useful as a PK1 receptor antagonist.
Another aspect of the invention is a method of monitoring the biological activity of a PK1 receptor in an animal.
These and other aspects and advantages of the invention will become apparent in light of the description below.